It's not new at all. I have used the [[square brackets]] for years. It has been most helpful when I wanted to use an image as a bullet point, keeping it fully inline with the following text.
Also, there is no need at all when using the {{curly braces}} to limit yourself to s, m, or l. I almost always set a pixel limit for the size parameter.
Both methods allow for alt text to allow those using screen readers to get an explanation of what an image is, rather than just know an image is there.